In fabricating a semiconductor device, a lithography technology using deep ultraviolet (DUV) light with a wavelength of 193 nm and ArF gas as a light source has been predominantly used pursuant to the demand for miniaturization, thereby obtaining a fine pattern of about 40 nm.
Further, combining the above-described photolithography technology using the light with the wavelength of 193 nm (ArF), as a basic technology, with a self-aligned double patterning (SADP) technology enables achievement of a miniaturization down to about 20 nm.
Meanwhile, a directed self-assembly (DSA) technology using a block copolymer has been proposed as a fine pattern forming technology which does not require an exposure apparatus.
In the DSA technology, for example, a block copolymer in which chains of A polymer and B polymer are bonded to each other at their ends is initially applied onto a substrate. Next, if the substrate is heated, the chains of the A polymer and B polymer randomly dissolved in a solid are subjected to phase separation, so that the regions of the A polymer and B polymer are regularly arranged. Then, the block copolymer is patterned by removing any one of the regions of the A polymer and B polymer to form a mask with a predetermined pattern. An example of the block copolymer includes a copolymer in which polystyrene (PS) and polymethyl methacrylate (PMMA) are bonded. In such block copolymer, a fine pattern up to 10 nm may be formed.
However, a photoresist for 193 nm exposure has a structurally insufficient strength. In this case, if the photoresist is formed in a fine pattern, there is a risk that the pattern may collapse due to wet development. Further, the roughness (e.g., line edge roughness (LER) or the like) of the pattern increases due to image blur caused by the wet development. Furthermore, the photoresist film may have a roughened surface due to low resistance to dry etching (i.e., plasma etching) conducted after the formation of the pattern, or disappearance of the film may occur due to low mask selectivity. This may cause various problems, e.g., deterioration in shape of an etched pattern.
Additionally, even in the DSA technology, the pattern may collapse in the wet development. Further, the mask selectivity being low in an etching process may cause problems to obtain a desired pattern. Furthermore, it is required to form a guide pattern for obtaining the desired pattern. However, variations of the guide pattern affect the pattern to thereby make the process difficult.